1. Field of the Invention
The present invention relates to a panel assembly structure, an integrated circuit mounting tape, and a manufacturing method thereof. The present invention relates, in particular, to a panel assembly structure in which an output terminal comprised of a part of an output side wiring line of a flexible wiring board is connected to an electrode terminal formed at a peripheral portion of a panel, and an input terminal comprised of a part of an input side wiring line of the flexible wiring board is connected to an electrode terminal of a wiring board for supplying a signal to an integrated circuit for driving the panel. The present invention also relates to an integrated circuit mounting tape in a state in which a substrate of the flexible wiring board extends in one direction and a manufacturing method thereof.
2. Description of the Prior Art
Among various sorts of panels implemented by EL (Electroluminescence), plasma, liquid crystals, a line sensor, a line printer and the like, the liquid crystal display (LCD) panel will be described as an example. FIG. 16 shows a perspective view of a prior art LCD device, while FIG. 17 shows a sectional view of the device taken along a line XVII--XVII in FIG. 16.
As shown in FIG. 16, the above-mentioned LCD device includes a LCD panel 101 and flexible wiring boards 104 and 105 where drive ICs (integrated circuit chips) 102 and 103 for driving the display panel 101 are mounted respectively on substrates 140 and 141 made of polyimide resin or the like. There are further provided a control board 107 for outputting a control signal and the like for driving the LCD panel 101 and transmitting the control signal to each flexible wiring board 105, and a wiring board 106 for transmitting the control signal to each flexible wiring board 104.
As shown in FIG. 17, the LCD panel 101 is formed by sealingly filling liquid crystals 110 into a space between a pair of glass substrates 108 and 109, and image display can be effected in the area in which the liquid crystals 110 are sealedly filled. A plurality of electrode terminals 112 comprised of a single layer or a multiplicity of layers made of such materials as ITO (Indium Tin Oxide), Ti, Ta, Mo, Al and TaN are arranged on a peripheral portion 111 of one glass substrate 108.
Each flexible wiring board 104 has a rectangular film-like substrate 140. As shown in FIG. 18, a through hole 142 having plane (length and width) dimensions greater than plane dimensions of the drive IC 102 is provided in an approximate center portion of a substrate surface 140s. An output side wiring line 114a and an input side wiring line 114b each connected to the drive IC 102 are provided on the substrate surface 140s. Portions 114e and 114f that belong respectively to the output side wiring line 114a and the input side wiring line 114b and are located on the peripheral side of the substrate surface 140s serve respectively as an output terminal and an input terminal of the flexible wiring board 104. On the other hand, as shown in FIG. 17, the output side wiring line 114a and the input side wiring line 114b are connected respectively to an output side electrode 113a and an input side electrode 113b of the drive IC 102 at their portions 114c and 114d that extend inside the through hole 142. An amount of protrusion 1b from the substrate surface 140s of the output side wiring line 114a and the input side wiring line 114b is set to a value of 1.8.times.10.sup.-2 mm or more. In an area where input terminals 114f are arranged on the substrate surface 140s is provided a slit 115 that penetrates the substrate 140. Each flexible wiring board 105 has approximately the same construction as that of the flexible wiring board 104.
The wiring board 106 is provided with an electrode terminal 117 that is connected to a bus line 116 and corresponds to the input terminal 114f of the flexible wiring board 104.
In a state of assembly, the electrode terminal 112 at the peripheral portion 111 of the LCD panel 101 and the output terminal 114e of the flexible wiring board 104 are connected with each other via an anisotropic conductive film 118. On the other hand, the input terminal 114f of the flexible wiring board 104 and the electrode terminal 117 of the wiring board 106 are connected with each other by means of solder 119. In detail, as shown in FIG. 19, the electrode terminal 112 of the LCD panel 101 and the output terminal 114e of the flexible wiring board 104 are connected with each other by heating or like means with interposition of the anisotropic conductive film 118 while receiving a pressure from a pressure head 137a on a stage 137b. Such an assembling technique is disclosed in Semiconductor World, special number, '93, new liquid crystal display process techniques, pp. 249-252, "driver IC assembling technique".
FIG. 20 shows another assembly structure of an LCD panel (Japanese Patent Laid-Open Publication No. HEI 4-242721). The LCD device shown in FIG. 20 includes an LCD panel 120, a flexible wiring board 122 mounted with a drive IC 121, and a wiring board 123 for transmitting a control signal to the drive IC 121. The LCD panel 120 is formed by sealingly filling liquid crystals 126 into a space between a pair of glass substrates 124 and 125, and a plurality of electrode terminals 128 are formed at a peripheral portion 127 of one glass substrate 125. The wiring board 123 is integratedly mounted to a peripheral portion 127 of the one glass substrate 125. The flexible wiring board 122 has an output side wiring line 133a, an input side wiring line 133b, and a protection film 134 on a film-like substrate 132 having no through hole. The output side wiring line 133a and the input side wiring line 133b are connected respectively to an output side electrode 122a and an input side electrode 122b of the drive IC 121 via an anisotropic conductive film (not shown) at their portions 133c and 133d exposed inside an opening of a protection film 135. The wiring board 123 has an electrode terminal 129 for transmitting a control signal to the drive IC 121 on its surface 123a mounted to the peripheral portion 127 of the glass substrate 125 of the LCD panel 120.
Then, an electrode terminal 128 at a peripheral portion 127 of the LCD panel 120 and an output terminal 133e comprised of a part of the output side wiring line 133a of the flexible wiring board 122 are connected with each other via an anisotropic conductive film (not shown). On the other hand, an input terminal 133f comprised of a part of the input side wiring line 133b of the flexible wiring board 122 and an electrode terminal 129 of the wiring board 123 are connected with each other via an anisotropic conductive film (not shown).
A pitch of the connection portion between the glass substrate 125 and the flexible wiring board 122 is set to, for example, 1.6.times.10.sup.-1 mm, a pitch of the connection portion between the flexible wiring board 122 and the drive IC 121 is set to, for example, 2.3.times.10.sup.-1 mm, and a pitch of the connection portion between the flexible wiring board 122 and the wiring board 123 is set to, for example, 0.7 mm.
Conventionally, as shown in FIG. 21, when terminals of two substrates, for example, the terminals of the drive IC 121 and the terminals of the slitless flexible wiring board 122 are connected with each other, positional reconditioning is effected by confirming alignment marks (not shown) of both the substrates 125 and 122 by means of two cameras 130 and 131, and thereafter the flexible wiring board 122 is moved by a specified length L. By the above-mentioned operation, the board 122 is superposed on the drive IC 121, so that the terminals are made to face each other. It is to be noted that sometimes only one camera is used to recondition the position of one substrate.
Such a thin type panel for use in a display, a sensor or the like as represented chiefly by an LCD panel, has the advantageous features of thin configuration, small size, light weight, low power consumption, and so forth in comparison with a display panel such as a cathode ray tube. For the above reasons, there has been a growing demand for using such a thin type panel in portable television sets, personal computers, pen input type electronic pocketbooks, in-car displays, industrial use displays, image readers, and so forth. Meanwhile, each thin type panel has been required to achieve further improvement of the performance thereof as a high-class information display device or an image reader, finer image display, and reduction in dimensions and cost by high-density assembling of components on the periphery of the display panel. Therefore, drive IC mounting technique has acquired greater importance.
If the above-mentioned demands are reflected on the prior art assembly structure shown in FIG. 17, there are required pitches of not greater than 0.1 mm, 8.0.times.10.sup.-2 mm and 0.4 mm respectively in the connection portion between the LCD panel 101 and the flexible wiring board 104, the connection portion between the flexible wiring board 104 and the drive IC 102, and the connection portion between the flexible wiring board 104 and the wiring board 106. Responding to the demands, some components such as a connection material are now under development so as to conform to a fine pitch.
However, in order to achieve the above-mentioned high-density assembling at a fine pitch stably with good mass-productivity, there are demanded, in addition to development of an appropriate connection material, the following requirements of:
(1) improving etching accuracy of the wiring lines 114a and 114b of the flexible wiring board 104; PA1 (2) improving accuracy in aligning boards; and PA1 (3) suppressing possible misalignment between mutually opposite electrode terminals attributed to a difference in coefficient of thermal expansion between boards made of different materials and slip of a connection material when it is melted. PA1 (1) that, when the drive IC 121 is aligned by a system as shown in FIG. 21 or the like in being mounted onto the flexible wiring board 122, a poor positional alignment accuracy results due to a misalignment in the positional reconditioning between the cameras 130 and 131 and a mechanical variation in amount of movement L; and PA1 (2) that, when the drive IC 121 is connected to the flexible wiring board 122, there easily occur a misalignment between the mutually opposite terminals due to a difference between coefficients of thermal expansion of the drive IC 121 and the flexible wiring board 122 and a reduction in reliability at the connection portions after the connecting process due to the influence of a residual stress.
In order to improve the etching accuracy of the flexible wiring board 104 (the above-mentioned requirement (1)), as known by persons skilled in the art, the amount of protrusion 1b from the substrate surface 140s of the wiring lines 114a and 114b is required to be reduced to, for example, 1.8.times.10.sup.-2 mm or less. However, when the amount of protrusion 1b is set to 1.8.times.10.sup.-2 mm or less, since the portions (terminals) 114c and 114d of the wiring lines 114a and 114b are protruding inside the through hole 142 without being supported by the substrate 140, there occurs a problem that the terminals 114c and 114d are bent in the manufacturing processes. Consequently, the above causes an increased number of cases of shortcircuit of the terminals 114c and 114d and an increased number of cases of imperfect connection of the terminals 114c and 114d with the output side electrode 113a and the input side electrode 113b of the drive IC 102, resulting in a reduced yield and a difficulty in fine-pitch connection.
Furthermore, since the input terminals 114f of the flexible wiring board 104 and the electrode terminals 117 of the wiring board 106 are connected with each other via solder 119, there has not been achieved fine-pitch connection at a pitch of not greater than 0.6 mm at the mass production level.
Further, the prior art assembly structure as shown in FIG. 20 has the problems: